The present invention relates to a coil to be used in and being a component of a device for contactless noninvasive comminution of concrements in the body of a living being; such a device generally includes a shockwave generator that is oriented towards the target area in the body of said being; in one more specific configuration the generator includes a flat coil, cooperating with a membrane which in turn is positioned to provide vibrations into a liquid filled cavity whereby particularly a brief current pulse is applied to the coil and will cause the membrane to produce a shockwave.
European patent application EP 275427 describes and discloses a shockwave tube including a coil carrier made of a ceramic material. One front end of this coil carrier includes a flat coil being of a single wire configuration and being bonded to that front side by means of a synthetic resin. An insulating foil is disposed between the flat coil and the membrane whereby during manufacture the coil and the membrane are forced against each other to in fact establish a structural unity. As stated the single wire coil is spirally coiled and owing to its embedment in the synthetic resin an additional spacing is introduced between the outer surface of the wire and the membrane.
In order to provide a shockwave a short electric voltage pulse of high amplitude is applied to the coil, this energy originates from a capacitor that has been charged previously and is rapidly discharged into the coil. The resulting electromagnetic field causes the adjacent membrane to be pushed away in an impact fashion and that rapid displacement of the membrane produces a shockwave in the adjoining liquid. The insulating foil is simply provided in order to avoid a voltage breakthrough between the coil and the membrane since the membrane is made of metal. A maximization of the pressure for the shockwave is obtained by selecting the distance between the coil and the membrane as small as possible and the amplitude of the current pulse is as high as possible but for reasons of the insulation a certain spacing and certain insulation has to be maintained.